Numerical simulation has become an indispensable tool for the design and optimization of photolithographic processes. Because the semiconductor industry now relies heavily on these tools, it is necessary to be able to benchmark their accuracy - as feature sizes continue to shrink, the numerical error in these simulators must decrease as well. Fortunately, there is a large body of literature from the optics community that can be used to benchmark the absolute accuracy of an aerial image calculation. We present a suite of closed-form solutions that are particularly relevant to optical lithography simulation. Our tests include solutions for both scalar and vector imaging models and for imaging with and without aberrations. These tests will be used to demonstrate how to identify many of the common numerical problems that can arise when performing aerial image calculations, and the closed-form solutions will be outlined in a form that will allow the tests to be applied to any aerial image simulator. Specific results will be presented for PROLITH and SPLAT. Both of these simulators give results that are in agreement with the closed-form test problems.